Catalyst for the preparation of ethylene and vinyl chloride from ethane

ABSTRACT

Ethane is reacted with oxygen and a chlorine source in the presence of a solid solution catalyst containing iron cations stabilized with lanthanum and/or lanthanides to yield ethylene, vinyl chloride, and other valuable by-products. Conversion of ethane to products approaches 100 percent, ethylene is prepared in up to 90 mole percent yield, and the combined yield of ethylene, vinyl chloride, and ethyl chloride is up to 95 mole percent.

This is a division of application Ser. No. 669,896, filed Mar. 24, 1976,now U.S. Pat. No. 4,102,935.

BACKGROUND OF THE INVENTION

Vinyl chloride (CH₂ ═CHCl) is prepared using a number of well knownprocesses. Two familiar processes are (1) the hydrochlorination ofacetylene and (2) the oxychlorination of ethylene to form dichloroethanewhich in turn is dehydrohalogenated to form vinyl chloride (see C. A.Schildknecht, Vinyl and Related Polymers, John Wiley and Sons, Inc.,N.Y., N.Y. (1952), pages 388-390, and U.S. Pat. No. 2,847,483). Asacetylene is more expensive then ethylene, the latter process iseconomically favored, and much activity is noted in this art area (seeU.S. Pat. Nos. 3,634,330; 3,454,663; 3,448,057; and 3,624,170).Ethylene, in turn, can be prepared by the oxydehydrogenation of ethane(see U.S. Pat. No. 3,769,362). Although high yields of ethylene areparticularly desired, processes which use ethane as a feed stock canproduce not only ethylene but also can directly produce vinyl chlorideand other valuable products such as ethylene dichloride, ethyl chloride,and the like. The ethylene, ethylene dichloride, and ethyl chloride canbe readily reacted to form more vinyl chloride.

The present invention is directed to an improved process for thepreparation of ethylene and vinyl chloride from ethane which processemploys a solid solution catalyst containing iron stabilized withlanthanum and/or lanthanides. This catalyst exhibits improved activityand/or long lifetime. Catalysts containing iron or lanthanum are knownto the art; see U.S. Pat. Nos. 3,907,713; 3,849,339; 3,769,362;3,703,593; 3,658,934; 3,658,933; 3,207,809; 2,847,483; and 2,674,633;and British Pat. No. 1,039,369. However, none of these patents disclosesa solid solution catalyst. An article in the Journal of The AmericanCeramic Society, Vol. 43, No. 7 (1960), page 367, discloses compounds oflanthanum and iron; recently issued U.S. Pat. No. 3,904,553 disclosescertain specific solid solutions as having activity as catalysts.

SUMMARY OF THE INVENTION

The invention comprises an improved catalyst and process for thepreparation of ethylene and vinyl chloride from ethane. The catalyst isa solid solution catalyst containing iron cations substituted forcations of the host lattice, which catalyst is stabilized with lanthanumand/or lanthanides. Use of the catalyst in the process of the inventionproduces yields of up to 90 mole percent of ethylene and up to 95combined mole percent of ethylene, ethyl chloride, and vinyl chloride.The catalysts can remain active for up to 200 hours without substantialloss of iron.

DETAILED DESCRIPTION OF THE INVENTION

Ethane is reacted with oxygen and a chlorine source and in the presenceof a solid solution catalyst containing iron stabilized with lanthanumand/or lanthanides to prepare ethylene, vinyl chloride, and othervaluable by-products. Depending upon feed and reactor conditions, about25 to 90 mole percent yield of ethylene and up to a 95 mole percenttotal yield of ethylene and vinyl chloride can be obtained. Conversionof ethane to products can approach 100 mole percent.

In the process, ethane, oxygen, and a chlorine source are placed into areactor vessel containing a solid solution catalyst of the invention.The process contemplates the use of standard techniques concerning thetype of operation, reactor size and design, and the like. The processcan be operated as a batch process, but is preferably conducted as acontinuous process wherein reactants and products are continuously addedand withdrawn. The solid solution catalyst can be fixed in a bed, it canbe supported, or it can be present as particles that can readilyfluidize during operation. A preferred embodiment of the process is toemploy the solid solution catalyst in particulate form that willfluidize in the process thereby establishing maximum contact with thereactants. Such processes are known as fluid bed processes, and thereactors designed for such as known as fluid bed reactors. A typicalreactor is designed such that one or more gaseous reactants isintroduced in the reactor below the catalyst bed, and the gaspressurized through the bed lifting and suspending the catalyst in thereactor volume. Other reactants can be added at appropriate levelsabove, below, or any point in the fluid catalyst bed. Normally, productsare withdrawn from the top portion of the reactor and collected orfurther treated as desired.

Although the process contemplates the use of known operating techniquesand reaction conditions, certain conditions are herein stated as usefuland practical. The reactants comprise ethane, oxygen (usually used inthe form of air), and a chlorine source. The chlorine source ispreferably hydrogen chloride gas. Using one mole of ethane as a basis,the hydrogen chloride is used at from about 0.1 mole to about 10 molesor more. More preferably, the hydrogen chloride is used at a level offrom about 0.5 mole to 5 moles per mole of ethane. In general, as ahigher ratio of hydrogen chloride to ethane is used, the yield of vinylchloride and other chlorinated products increases and the yield ofethylene decreases. However, levels of use of hydrogen chloride above 5moles per mole of ethane also increase the amount of hydrogen chlorideto recycle. Excellent results have been obtained using about 1 to about4 moles of hydrogen chloride per mole of ethane. As both ethylene andvinyl chloride can be prepared in significant amounts using thecatalysts and as the yield of ethylene to vinyl chloride is highlydependent upon the hydrogen chloride to ethane ratio in the reactantfeed, the process can be termed either an oxydehydrochlorination processto prepare ethylene or an oxychlorination process to prepare vinylchloride.

Oxygen, preferably in the form of dry air, is used at from about 0.1mole to about 1.5 moles of oxygen to one mole of ethane. A morepreferred level is from about 0.5 mole to about 1 mole. The use oflevels of oxygen of about 1 mole per mole of ethane is preferred in anoxychlorination process. In an oxydehydrochlorination process, excellentresults have been obtained using a level of oxygen of about 0.5 to 0.6mole per mole of ethane.

Ethane, oxygen, and hydrogen chloride are put into the reactor asreactants. Temperature of the reaction ranges from about 400° C. toabout 650° C., and more preferably from about 475° C. to about 600° C.Materials withdrawn from the reactor in the product stream compriseethylene, vinyl chloride, chlorinated products such as ethylenedichloride and ethyl chloride, carbon oxides (CO and CO₂), water, andunreacted ethane and hydrogen chloride.

The improved feature of the process of the invention is the use of asolid solution catalyst containing iron cations substituted for cationsin the host lattice which catalyst is stabilized with lanthanum and/orlanthanides. The catalyst is basically a solid solution of iron cationsin a host lattice. This is in contrast to catalysts wherein an activeingredient such as cupric chloride or iron oxide is merely absorbed ontothe surface of a support structure or material. The difference iscrucial and can be distinguished both in the physical state of thecatalyst and in the activity of the catalyst.

The solid solution catalyst is a true solution wherein iron cations aresubstituted for host lattice ions in the catalyst structure. An X-raydiffraction pattern of a solid solution catalyst is characteristic ofthe diffraction pattern of the host lattice. For example, a solidsolution catalyst of Fe₂ O₃ in α-Al₂ O₃ will exhibit an X-raydiffraction pattern characteristic of α-Al₂ O₃. In contrast, if Fe₂ O₃is merely absorbed onto α-Al₂ O₃, the X-ray diffraction pattern willshow the presence of both Fe₂ O₃ and α-Al₂ O₃.

A distinguishing feature of the solid solution catalysts of theinvention, i.e., solid solution catalysts containing iron and stabilizedwith lanthanum and/or lanthanides, is in the increased retention of ironupon use. For example, an α-Al₂ O₃ solid solution catalyst containingiron cations and stabilized with lanthanum cations used at reactionconditions of 1 mole ethane/0.6 mole oxygen/1.5 mole hydrogen chloridelost about 3% by weight of its original iron content after about 100hours of use. In contrast, a catalyst which is a simple solid solutionof iron in α-Al₂ O₃ lost about 4% by weight of its iron content underthe same conditions. In further contrast, a catalyst comprised of ferricoxide merely absorbed onto Al₂ O₃, operating under the same set ofconditions, lost over 8% by weight of its original iron content afterabout 100 hours of use.

The solid solution catalysts containing iron cations can be of differenttypes. The iron exists as ferric (Fe⁺³) and/or ferrous (Fe⁺²) ions. Theferric ion is the active ion in the catalyst. However, as the ferrousion can oxidize to a ferric ion in the process, the use of solidsolution catalysts containing ferrous ions are within the scope of theinvention.

In the solid solution catalyst containing iron cations there is directsubstitution of iron ions for host lattice ions. An example of thiscatalyst is (Fe_(x) ⁺³ M_(2-x) ⁺³)O₃ wherein x is greater than 0 andless than 2 and M is a metal such as Al or Cr. An example of this is asolid solution catalyst of ferric oxide (Fe₂ O₃) in aluminum oxide (Al₂O₃). As the ferric ion is much greater in size than an aluminum +3 ion,the solubility of the ferric ion in aluminum oxide is limited. Hence,the solid solution catalysts of the example wherein M is aluminumencompass materials of the formula wherein x has an upper limit of about0.15.

The solid solution catalyst containing iron is stabilized with lanthanumand/or a lanthanide. Although the lanthanum or lanthanide is an integralpart of the catalyst, it is believed that the lanthanum or lanthanidedoes not enter into solid solution with the host lattice as does theiron. Characterization of the catalysts of this invention will bediscussed further in a subsequent section of the application.

The lanthanum and lanthanides can be employed in the solid solutioncatalysts singly or as mixtures of the metals. The lanthanides areelements 58 to 71 of the Periodic Table. More preferably, thelanthanides used are Cerium, Praeseodymium, Neodymium, and Erbium. Apreferred catalyst consists of a solid solution catalyst containing ironand stabilized with lanthanum, praeseodymium or neodymium. Excellentresults have been obtained using a catalyst of Fe₂ O₃ in α-Al₂ O₃stabilized with lanthanum.

Solid Solution Catalyst Identification and Characterization

The solid solution catalysts of the invention contain iron and haveX-ray diffraction patterns characteristic of the host lattice material.Solid solutions are known to exist (see C. S. Barrett, Structure ofMetals, Crystallographic Methods and Principles, and Data, 2nd Ed.,McGraw-Hill Book Co., Inc., N.Y., N.Y. (1952), at pages 220 et seq.).

The catalyst is first identified and characterized by analyzing it todetermine what elements it contains. This can be done using well knowntechniques such as chemical analysis, atomic absorption spectroscopy,X-ray fluorescence spectroscopy, and optical microscopy. For example,the solid solution catalyst of iron oxide in aluminum oxide, stabilizedwith lanthanum would show iron, lanthanum, aluminum, and oxygen to bepresent in the catalyst. The presence and quantity of iron in thecatalyst can be readily determined using a standard method of chemicalanalysis such as the dichromate method for the determination of iron.The amount of iron in the solid solution catalysts is limited by thesolubility of the ions in the host lattice. The solid solution catalystscan contain from about 0.1 percent to 20 percent by weight and morepreferably from about 0.5 percent to about 10 percent by weight of ironin the catalyst expressed as iron oxide. The catalyst can contain asimilar level of lanthanum and/or lanthanide expressed as the oxide.

The second step of identification and characterization involves runningan X-ray diffraction scan on the catalyst. The X-ray diffraction scanwill show a pattern of peaks, which peaks have positions and intensitiesdistinctive of the crystalline phases which are present. The X-raydiffraction peak positions and intensities of the catalyst can becompared to peak positions and intensities of known crystalline phasesthat are published (in the ASTM Powder Diffraction File, for example),or that are experimentally obtained. For example, a catalyst comprisedof iron oxide merely impregnated on aluminum oxide will have an X-raydiffraction pattern of peak positions showing the distinct peakpositions and intensities of iron oxide and aluminum oxide crystallinephases.

In contrast, the X-ray diffraction pattern of a solid solution catalystcontaining iron shows the positions of the X-ray diffraction peaks inthe solid solution catalyst to be shifted from the peak positions in theX-ray diffraction pattern of the host lattice. The shift in peakpositions may be accompanied by changes in the relative intensities ofthe peaks, but the intensity changes are generally small.

The shift in X-ray diffraction peak positions when solid solutions areformed results from the expansion (or contraction) of the dimensions ofthe unit cell of the crystalline phase of the host lattice. Thedimensions of the unit cell of the host lattice are changed due to thesubstitution of iron cations for cations of the host lattice. If thecation is larger than the cation it displaces, the unit cell dimensionswill increase in size to accommodate the larger cation. The amount ofexpansion (or contraction if the iron cation is smaller than the hostlattice cation it displaces) of the unit cell dimensions can bedetermined by calculating the lattice parameters of the unit cell of thesolid solution phase and comparing these lattice parameters to thelattice parameters of the unit cell of the host. A change in latticeparameters due to iron substitution in a crystalline host lattice isfrequently in accordance with Vegard's law (see page 221 of theabove-cited reference). Since a change in the lattice parameters causesa change in the X-ray diffraction peak positions, a quick comparison ofthe X-ray diffraction pattern of the catalyst and the pattern of thehost lattice will show whether a solid solution catalyst has beenprepared.

Alternately, a more accurate method of confirming the preparation of asolid solution catalyst is to experimentally run X-ray diffraction scansof the prepared catalyst and of the host lattice and then calculate thelattice parameters of each. If the values obtained for the latticeparameters of the catalyst and host lattice are different, a solidsolution catalyst has been prepared. If the geometry and dimensions(lattice parameters) of the unit cell of the host lattice is not known,it can be determined using established methods for indexing andinterpreting X-ray diffraction patterns (see L. V. Azaroff and M. J.Buerger, The Powder Method In X-Ray Crystallography, McGraw-Hill BookCo., Inc., N.Y., N.Y. (1958), chapters 6 to 13). The high 2θ values(where θ is the Bragg angle) are normally used to calculate the latticeparameters.

In the case of a solid solution catalyst stabilized with lanthanumand/or a lanthanide, the X-ray diffraction pattern will clearly show thepresence of the solid solution, which is the primary crystalline phase,and will additionally show the presence of crystalline lanthanum and/orlanthanide compounds which are present in detectable amounts. Forexample, in the case of a solid solution catalyst of Fe₂ O₃ in α-Al₂ O₃stabilized with lanthanum, the X-ray diffraction pattern will show thepresence of the Fe₂ O₃ in α-Al₂ O₃ solid solution crystalline phase andcrystalline compounds of lanthanum such as La₂ O₃ and LaAlO₃.

In summary, the solid solution catalysts of the invention can beidentified and characterized by (1) the presence of iron and lanthanumand/or lanthanides in the catalyst, and (2) the X-ray diffractionpattern of the catalyst. The iron is present as cations substituted inthe host lattice for cations of the host lattice. The iron content canbe measured using standard analysis techniques. The X-ray diffractionpattern of the solid solution catalyst will exhibit peak positionscharacteristic of the host lattice but shifted due to the presence ofthe iron cations in the host lattice. Lattice parameters calculated forthe host lattice and the solid solution catalyst will differ. The X-raydiffraction pattern of the solid solution catalysts of the inventionwill exhibit extraneous peaks in the pattern due to formation ofcrystalline compounds other than the solid solution catalyst itself,such as lanthanum oxide or lanthanide oxides.

Preparation of Solid Solution Catalysts

The solid solution catalysts used in the Examples were prepared by firstimpregnating a host lattice precursor with an iron salt and a lanthanumsalt and/or a salt of a lanthanide that yields the oxides upon heating,then heating the impregnated host lattice precursor to about 550° C.followed by heating to 1200° C. or more. The first heat treatmentconverts the salts to oxides, and initiates conversion of the hostlattice precursor to the host lattice. The second heat treatmentcompletes the formation of the host lattice and produces a rearrangementof the metal atoms between the metal ions in the host lattice and theiron ions. The catalyst prepared is a solid solution catalyst containingiron, stabilized with lanthanum and/or lanthanides, having a distinctiveX-ray diffraction pattern.

The solid solution catalyst can be prepared in other different ways.Another method is to physically admix iron oxide, lanthanum or alanthanide oxide, and the host lattice material and heat the mix toallow dissolution and substitution of the iron ions for those of thehost lattice, and formation of the stabilized catalyst. Heatingconditions vary for the nature of the host lattice employed, buttypically are above about 1100° C.

A third method of preparation is to use the so-called sol-gel processwherein an iron salt, lanthanum and/or lanthanide salt, and a saltprecursor of the host lattice are mixed together as solutions and a baseis added to co-precipitate out a mixture of the corresponding hydratedoxides. For example, ferric nitrate, lanthanum nitrate, and aluminumnitrate can be dissolved in water and ammonium hydroxide added to thesolution to co-precipitate a mixture of hydrated iron, lanthanum, andaluminum oxides. The mix is then heated to above about 1100° C. toperfect dissolution and substitution of the iron ions for aluminum ions.

A fourth method is to dissolve a lanthanum or lanthanide salt in asolvent such as water or ethanol and use the solution to impregnate apreformed solid solution catalyst then dry and heat the mix to cause themetal salt to decompose upon heating to yield the oxide.

In all of these methods a metal oxide precursor can be used in place ofthe metal oxide per se. The precursor, which is typically a salt of themetal, decomposes on heating to yield the oxide form of the metal.Examples of iron oxide precursors are iron chloride, iron sulfate, ironformate, iron oxalate, iron citrate, iron nitrate, and the like.Precursors of the oxides of lanthanum or lanthanides and of the selectedmetals can also be employed. Examples of lanthanum oxide precursors arelanthanum nitrate, lanthanum chloride, lanthanum sulfate, lanthanumoxalate, and the like.

The solid solution catalysts of the invention can be used in the processin the form of a fixed bed, a fluidized bed, on a fixed support, on afluidized support, or in a number of ways well known to the art.Although in the examples the process used is a fluidized bed process, itis understood that other well known techniques can be employed. Thefollowing Examples are given to further illustrate the invention.

EXAMPLES Oxydehydrochlorination Process

Solid solution catalysts were used in an oxydehydrochlorination processto react ethane to ethylene and small amounts of vinyl chloride. Thereactions were conducted in a fluid bed reactor wherein the ethane,oxygen used in the form of air, and anhydrous HCl were premixed at a setmolar ratio of reactants and the mixture fed into a heated reactor nearthe bottom. The catalyst used was in the form of particles of a sizepassing between 80 mesh and 325 mesh screens. Contact times in thereaction were from about 4 seconds to about 10 seconds. Products werewithdrawn from the top of the reactor as gases, scrubbed with water andanalyzed using a gas chromatograph. The process was run as a continuousprocess for times of 1 hour up to 300 hours or more per run.

The following examples detail experiments conducted using various moleratios of reactants, various temperatures and times of reaction, anddifferent solid solution catalysts.

EXAMPLE I

Experiments were conducted to compare ethane conversion and yield ofethylene and vinyl chloride obtained between a catalyst of thisinvention and an impregnated catalyst. Both catalysts contained about 2%by weight of Fe₂ O₃. The catalyst of the invention was prepared byadding a solution of 31.9 grams of La(NO₃)₃ --6H₂ O and 29.75 grams ofFe(NO₃)₃ --9H₂ O dissolved in about 400 milliliters of ethanol to 431.1grams of Al₂ O₃ --3H₂ O (sold by Alcoa Co. as C--31) and evaporating offthe ethanol. The mixture was then heated at 550° C. for 16 hours todehydrate the alumina trihydrate and to decompose the ferric nitrate andlanthanum nitrate to ferric oxide and lanthanum oxide. The catalyst wasthen further heated at 1200° C. for 16 hours to cause formation of thesolid solution catalyst.

The impregnated catalyst employed in the example was prepared byimpregnating aluminum oxide with a solution of ferric nitrate, dryingthe mix and then heating the mix for 16 hours at 550° C. The preparationis similar to the preparation of the solid solution catalyst except thatno heat treatment at 1200° C. was done. X-ray diffraction analysis ofthe impregnated catalyst showed two distinct phases, i.e., theimpregnated catalyst was a mixture of Fe₂ O₃ and Al₂ O₃.

The catalysts were placed into the reactor and the reactants fed intothe reactor at a mix of 1 mole ethane/0.6 mole of oxygen (as air)/1.5moles of anhydrous hydrogen chloride. Contact time throughout the runswas about 5 seconds. Temperature of reaction was 550° C. Results aregiven in the following tables.

    ______________________________________                                        Solid Solution Catalyst                                                                                   Total %                                           Mole %       % Yield of     Yield of                                          Time  Conversion           Vinyl  Ethylene and                                (Hrs.)                                                                              Of Ethane  Ethylene  Chloride                                                                             Vinyl Chloride                              ______________________________________                                        1.5   89.7       75.4      14.7   90.1                                        5     86.9       78.8      12.7   91.5                                        27    88.6       80.9      9.7    90.6                                        48    86.8       81.4      9.3    90.7                                        71    86.0       81.0      7.6    88.6                                        96.5  82.3       81.9      6.0    87.9                                        105   86.5       82.4      7.5    89.9                                        125   85.2       80.6      6.6    87.2                                        Impregnated Catalyst                                                                                      Total %                                           Mole %       % Yield Of     Yield Of                                          Time  Conversion           Vinyl  Ethylene and                                (Hrs.)                                                                              Of Ethane  Ethylene  Chloride                                                                             Vinyl Chloride                              ______________________________________                                        18.5  53.9       72.3      2.1    74.4                                        44    57.4       71.8      2.3    74.1                                        66.5  51.9       73.6      2.4    76.0                                        90.5  53.6       73.6      2.5    76.1                                        ______________________________________                                    

The data shows that the use of the solid solution catalysts of theinvention results in significantly higher mole percent conversion ofethane to products and higher yield of ethylene and vinyl chloride thanthe use of the impregnated catalysts.

The solid solution catalysts of the invention have excellent stability,showing activity for long periods of time when in use. The catalyst usedabove lost only 3.1% of its original iron content after 97 hours andonly 4.7% of its original iron content after 203 hours of use (A solidsolution catalyst containing iron but no lanthanum lost almost 4% of itsiron content in 100 hours of use at the same conditions). In contrast,the simple catalyst of iron oxide impregnated on aluminum oxide lost8.4% of its original iron content after 90 hours of use.

A further experiment using the 2% Fe₂ O₃ in Al₂ O₃ solid solutioncatalyst stabilized with 4% by weight of La₂ O₃ was run at a reactantfeed ratio of 1 mole ethane/0.5 mole oxygen/1.5 mole of hydrogenchloride and with a contact time of about 3 seconds in the reactor. Thefollowing results were obtained.

    ______________________________________                                               Mole % Conversion                                                                         % Yield Of                                                 Time (Hrs.)                                                                            Of Ethane     Ethylene Vinyl Chloride                                ______________________________________                                        1        80.4          85.4     7.4                                           18       80.8          89.6     6.4                                           43       85.3          87.4     7.8                                           66       85.6          87.8     7.5                                           91       83.9          86.7     6.1                                           163      88.6          86.5     7.1                                           ______________________________________                                    

EXAMPLE II

The weight of iron present (expressed as iron oxide) and the weightratio of iron present (expressed as iron oxide) to lanthanum present(expressed as lanthanum oxide) has an effect upon the mole percentconversion of ethane, the percent yield of ethylene and vinyl chloride,and/or the loss of iron by the catalyst. A series of experiments wererun using solid solution catalysts prepared having various weights ofiron and weight ratios of iron to lanthanum in the catalyst. The exactcatalysts used are described as follows:

    ______________________________________                                                 Weight % in Al.sub.2 O.sub.3                                                                 Weight Ratio of                                       Catalyst  Fe.sub.2 O.sub.3                                                                         La.sub.2 O.sub.3                                                                          Fe.sub.2 O.sub.3 /La.sub.2 O.sub.3           ______________________________________                                        A         1          8          1/8                                           B         1          2          1/2                                           C         2          4          1/2                                           D         4          8          1/2                                           E         4          2          2/1                                           F         10         4          2.5/1                                         ______________________________________                                    

The above catalysts were used in a fluidized bed reaction process forconversion of ethane to ethylene. The reactant feed ratio used was1/0.5/1.5 or 1/0.6/1.5 ethane/O₂ /HCl, temperature of the reaction was550° C., and contact times ranged from 3 to 5 seconds. Results are givenin the following table.

    __________________________________________________________________________                Mole % Conversion                                                                       % Yield Of   Percent                                    Catalyst                                                                           Time (Hrs.)                                                                          Of Ethane Ethylene                                                                           Vinyl Chloride                                                                        Iron Loss                                  __________________________________________________________________________    Feed Ratio = 1/0.5/1.5 (ethane/O.sub.2 /HCl)                                  A    67.5   15.4      50.2 0.9     --                                              138.5  24.6      45.4 1.5     --                                              210.5  53.6      64.8 1.4     --                                              306    22.9      38.5 0.7     0.0                                        B    71     29.8      36.2 5.0     --                                              142.5  21.0      33.0 1.1     --                                              242.5  19.7      24.9 0.2     --                                              312    34.5      70.9 3.9     0.1                                        C    71     86.0      81.0 7.6     --                                              125    85.2      80.6 6.6     --                                              203    72.0      77.9 2.7     4.7                                        D    68     74.4      84.9 3.9     --                                              130    63.5      81.5 2.2     --                                              222    36.7      70.3 0.6     --                                              295    41.5      71.3 2.3     6.5                                        E    56     71.9      79.6 7.2     --                                              136    43.4      70.5 3.0     4.4                                        Feed Ratio = 1/0.6/1.5 (ethane/O.sub.2 /HCl)                                  C    18     80.8      89.6 6.4     --                                              66     85.6      87.8 7.5     --                                              163    88.6      86.5 7.1     --                                         F    --     90.5      81.7 12.0    --                                         __________________________________________________________________________

The data shows that conversion of ethane and yields of ethylene andvinyl chloride increase significantly with the increase of iron in thecatalyst at least until about 2% by weight iron oxide. Increases withthe increase of iron oxide from 4% to 10% by weight are less dramatic.Increasing the weight ratio of La₂ O₃ to Fe₂ O₃ retards iron loss in thecatalyst.

EXAMPLE III

The reactant feed ratio used in the conversion process can varyconsiderably. The main effect of varying this ratio is to change theyields of ethylene and vinyl chloride obtained. Mole percent conversionof ethane is little effected. A series of experiments were conductedusing a solid solution catalyst (Catalyst F from Example II) in afluidized bed process with a contact time of about 4 seconds and at atemperature of 550° C. wherein the reactant feed ratio varied as 1ethane/0.6 to 1 oxygen/1.5 to 4 hydrogen chloride.

    ______________________________________                                        Mole %        % Yield Of    Combined Yield                                    Reactant                                                                              Conversion         Vinyl   Of Ethylene And                            Feed Ratio                                                                            Of Ethane Ethylene Chloride                                                                             Vinyl Chloride                              ______________________________________                                        (ethane/O.sub.2 /HCl)                                                         1/0.6/1.5                                                                             90.5      81.7     12.0   93.7                                        1/0.6/2.5                                                                             95.1      81.4     13.7   95.1                                        1/0.6/4 96.9      81.5     14.9   96.4                                        1/0.7/1.5                                                                             95.2      79.6     14.6   94.2                                        1/0.7/2.5                                                                             99.5      74.8     17.9   92.7                                        1/0.7/4 98.8      72.9     21.6   94.5                                        1/0.8/1.5                                                                             99.6      67.4     16.8   84.2                                        1/0.8/2.5                                                                             99.8      66.4     21.8   88.2                                        1/0.8/4 99.7      64.4     24.9   89.3                                        1/0.9/2.5                                                                             100       58.9     25.8   84.7                                        1/0.9/4 99.8      52.7     31.9   84.6                                        1/1/4   99.8      48.7     32.6   81.3                                        ______________________________________                                    

As the amount of HCl and O₂ are increased in a series, conversion ofethane generally increases and yield of vinyl chloride increases, whilethe yield of ethylene decreases. As the amount of O₂ is increased, thecombined yield of ethylene and vinyl chloride remains fairly constantuntil above about a 0.8/1 oxygen to ethane ratio.

EXAMPLE IV

The iron ions are the major active agent in the catalysts of theinvention. The major purpose of the lanthanum metal (or lanthanidemetal) is to inhibit loss of iron from the catalyst. The catalyst in theprevious examples was comprised of iron oxide and lanthanum oxide inaluminum oxide. This example shows the use of lanthanide metals in placeof lanthanum in the catalysts. Temperature of the reaction was 550° C.and contact time was 4 to 5 seconds. Reactant feed ratio was 1/0.6/1.5ethane/O₂ /HCl.

    ______________________________________                                                      Mole %  % Yield of                                                          Time    Conversion       Vinyl                                    Catalyst    (Hrs.)  Of Ethane Ethylene                                                                             Chloride                                 ______________________________________                                        2% Fe.sub.2 O.sub.3 in Al.sub.2 O.sub.3                                                   4       78.9      76.6   9.3                                      stabilized with                                                                           31.5    73.0      72.2   7.1                                      4% Er.sub.2 O.sub.3                                                                       57.5    22.8      40.8   1.3                                                  79.5    20.1      32.0   --                                       2% Fe.sub.2 O.sub.3 in Al.sub.2 O.sub.3                                                   29      77.2      78.1   5.8                                      stabilized with                                                                           49.5    79.0      76.7   5.1                                      4% Pr.sub.2 O.sub.3                                                                       77      50.8      64.6   3.1                                      2% Fe.sub.2 O.sub.3 in Al.sub.2 O.sub.3                                                   --      92.2      82.2   12.1                                     stabilized with                                                               4% Nd.sub.2 O.sub.3                                                           ______________________________________                                    

EXAMPLE V

The 2% iron oxide in α-aluminum oxide stabilized with 4% praeseodymiumoxide and 2% iron oxide in α-aluminum oxide stabilized with 4% neodymiumoxide catalysts described in the previous example were used in a seriesof experiments wherein the reactant feed ratio was varied. The processwas a fluidized bed process operating at 550° C. with a contact time ofabout 5 seconds.

    __________________________________________________________________________                                     Combined Yield                               Reactant Feed Ratio                                                                     Mole % Conversion                                                                       % Yield Of   Of Ethylene And                              (ethane/O.sub.2 /HCl)                                                                   Of Ethane Ethylene                                                                           Vinyl Chloride                                                                        Vinyl Chloride                               __________________________________________________________________________    2% Fe.sub.2 O.sub.3 in Al.sub.2 O.sub.3                                       stabilized with                                                               4% Pr.sub.2 O.sub.3                                                           1/0.25/0.5                                                                              44.0      93.9 2.8     96.7                                         1/0.5/0.5 73.5      82.7 4.3     87.0                                         1/0.5/1.5 90.0      85.2 11.0    96.2                                         1/0.5/4   90.8      87.2 9.4     96.6                                         1/0.7/4   99.8      65.5 27.6    93.1                                         1/0.9/4   99.6      46.8 38.9    85.7                                         2% Fe.sub.2 O.sub.3 in Al.sub.2 O.sub.3                                       stabilized with                                                               4% Nd.sub.2 O.sub.3                                                           1/0.5/1.5 90.1      85.9 10.0    95.9                                         1/0.6/1.5 96.6      78.2 16.0    94.2                                         1/0.7/1.5 97.7      71.6 18.8    90.4                                         1/0.7/4   99.8      65.8 26.8    92.6                                         __________________________________________________________________________

As in Example III which showed the use of the lanthanum stabilized solidsolution iron catalyst, as the amount of O₂ and HCl increased theconversion of ethane and yield of vinyl chloride increased and the yieldof ethylene decreased.

EXAMPLE VI

Combinations of lanthanum and lanthanide metals can be used with theiron oxide and aluminum oxide. Two catalysts were prepared containing0.5% cerium oxide and 1.3% cerium oxide by weight in a 4% lanthanumoxide stabilized 2% iron oxide in α-aluminum oxide catalyst. Thecatalysts were used in the ethane to ethylene conversion process at atemperature of 550° C. and about a 4 second contact time. Results areshown in the following table.

    ______________________________________                                                      Mole %  % Yield Of                                              Reactant Feed Ratio                                                                       Time    Conversion        Vinyl                                   (ethane/O.sub.2 /HCl)                                                                     (Hrs.)  Of Ethane Ethylene                                                                             Chloride                                 ______________________________________                                        2% Fe.sub.2 O.sub.3 in Al.sub.2 O.sub.3 stabilized with 4% La.sub.2           O.sub.3 and 0.5% Ce.sub.2 O.sub.3                                             1/0.5/1.5   --      83.9      82.9    9.3                                     1/0.6/1.5   --      93.2      77.5   12.9                                     1/0.7/4     --      99.0      73.4   19.8                                     2% Fe.sub.2 O.sub.3 in Al.sub.2 O.sub.3 stabilized with 4% La.sub.2           O.sub.3 and 1.3% Ce.sub.2 O.sub.3                                             1/0.6/1.5    24     77.5      79.3   9.5                                      1/0.6/1.5    52     70.2      78.3   7.1                                      1/0.6/1.5   100     65.0      75.1   5.4                                      1/0.6/1.5   118     61.4      74.3   4.7                                      ______________________________________                                    

EXAMPLE VII

The temperature of the ethane to ethylene conversion reaction has aneffect on conversion and yields obtained in the process. Generally,between the temperatures of 500° C. to 600° C., higher temperaturesincrease the mole % conversion of ethane and somewhat increase the yieldof ethylene. A reaction temperature of about 550° C. offers a goodbalance of mole % conversion of ethane and high ethylene yield andcombined yield of ethylene and vinyl chloride. The following resultswere obtained using a 2% Fe₂ O₃ in Al₂ O₃ catalyst stabilized with 4%Nd₂ O₃.

    __________________________________________________________________________    Reactant        Mole %             Combined Yield                             Feed Ratio                                                                             Temperature                                                                          Conversion                                                                          % Yield Of   Of Ethylene and                            (ethane/O.sub.2 /HCl)                                                                  (° C.)                                                                        Of Ethane                                                                           Ethylene                                                                           Vinyl Chloride                                                                        Vinyl Chloride                             __________________________________________________________________________    1/0.25/0.5                                                                             530    43.9  91.7 2.9     94.6                                                550    44.0  93.9 2.8     96.7                                                570    46.5  93.6 2.9     96.5                                       1/0.4/0.5                                                                              530    60.6  84.8 3.6     88.4                                                550    64.8  88.1 4.2     92.3                                                570    66.1  89.9 3.6     93.5                                       1/0.4/1.5                                                                              530    71.4  92.3 5.7     98.0                                                550    76.1  91.9 6.2     98.1                                                570    86.7  89.2 7.8     97.0                                       __________________________________________________________________________

We claim:
 1. A solid solution catalyst consisting essentially of ironcations substituted for aluminum cations in a host lattice of α-Al₂ O₃and having an iron content of from about 0.1 percent to about 20 percentby weight expressed as the oxide; stabilized with a total lanthanidecontent of from about 0.1 percent to 20 percent by weight expressed asthe oxide; and having an X-ray diffraction pattern having peak positionsdifferent than that of the host lattice, all weight percents based uponthe weight of the catalyst.
 2. A solid solution catalyst of claim 1wherein the iron content of the catalyst is from about 0.5 percent toabout 10 percent by weight of the catalyst, expressed as the oxide.
 3. Asolid solution catalyst of claim 2 consisting essentially of ironcations substituted for aluminum cations in a host lattice of α-Al₂ O₃,stabilized with from about 0.5 percent to about 10 percent by weightexpressed as the oxide of lanthanum, cerium, praeseodymium, neodymium,erbium, or mixtures thereof.
 4. The solid solution catalyst of claim 3consisting essentially of iron cations substituted for aluminum cationsin an α-Al₂ O₃ host lattice stabilized with lanthanum oxide.
 5. Thesolid solution catalyst of claim 3 which is stabilized with erbiumoxide.
 6. The solid solution catalyst of claim 3 which is stabilizedwith praeseodymium oxide.
 7. The solid solution catalyst of claim 3which is stabilized with neodymium oxide.
 8. The solid solution catalystof claim 3 which is stabilized with cerium oxide.